The present invention relates to a electrical connection for use with a heater cable in a well bore; more specifically, this invention claims an apparatus for connecting a electrical submersible pump cable to a heater cable to place the heater cable elements within a well bore distant from the source of electrical power for such heater cable.
There are many oilfield applications in which heating inside the well bore will enhance production. One type of down-hole heater consists of a single electrical conductor wire of high resistance (such as ni-chrome wire) which is placed concentrically inside a stainless steel, or other alloy metal tube (such as monel). To insulate the conductor from the outer tubing, an inert mineral insulation (MI) material (such as magnesium oxide) is often used. These down-hole resistance heaters are usually strapped to the production tubing, and power is supplied from the surface. In the case of oil wells, these heater cables are submerged in the oil-producing zone, and are used to raise the temperature of the oil, thereby lowering its viscosity to permit efficient flow of the oil to surface. In gas wells, these heaters can often be used to heat almost the entire length of the production tubing, to reduce the formation of scale, paraffin, and hydrates which can form in the production tubing and restrict or block flow.
Heaters of this type are usually powered by three-phase equipment at surface, so three individual heater tubes are typically strapped or banded to the production tubing. Close to surface, each of these tubes are connected to a “cold lead” section, or a section of tubing which is not meant to increase in temperature. Basically, the cold section consists of low resistance wires inside metal tubing. A cross-over type piece from the hot section to the cold section is assembled by the heater manufacturer, and installed prior to delivery.
The cold lead section typically passes through the surface wellhead, using metal ferrule type fittings. This arrangement works well for shallow well applications, in which the overall length of the hot and cold section is not more than 4,000 ft.
However, for deeper well applications, the manufacture of longer lengths of heater tubes is difficult, or impossible. At times, only a 300 foot section of pay zone in an oil well needs to be heated, but the pay zone is 7,500 feet below surface. It is not economical to manufacture a hot or cold section in these longer lengths.
The current patent application solves the above problem by providing a connector that will connect the three cold lead sections of a heater cable to the three individual wires from a typical Electrical Submersible Pump (ESP) cable, thereby providing a readily available solution to this problem of providing an electrical connection in high temperature, high pressure well bores.
ESP cable is much less expensive, easier to manufacture and procure than the MI Heater Cables. The connection of the present invention can allow for a short section of heater cable, a short section of cold lead cable, and a long length of ESP cable. ESP cable can be sealed off using several known means through the surface wellhead, providing an economical and efficient solution to the problem of increasing oil and gas production.